Continuously variable electroacoustic delay device

ABSTRACT

There is herein described a continuously variable electrical delay device wherein a beam of electrically charged particles impinge upon an electroacoustic delay element. By imposing a charge or electrical impulse on the surface of the delay element, an acoustic wave can be created therein. This acoustic wave and an associated electrical charge travel through the delay element to a pickoff terminal where a detectable output voltage is removed. The amount of time by which an input signal is delayed is continuously and accurately variable over a wide range of values by electronically varying the position at which the charged particle beam impinges upon the delay element with respect to the pickoff terminal.

United States Patent Inventors William J. Soul: Nashua;

David J. Whitney, Amherst, both 0!, N.H. [2 l] Appl. No. 767,429 [22] Filed Oct. 14, 1968 [45] Patented Aug. 31, 1971 [73] Assignee Sanders Associates, inc.

Nahum, N11.

[54] CONTINUOUSLY VARIABLE ELECTROACOUSTIC DELAY DEVICE 47 Claims, 7 Drawing Figs.

[52] 0.8. 315/18, 333/30 [51] Int. H01] 29/70 [50] I'leldofSearch 315/3, 18, 21; 333/30 [56] References Cited UNITED STATES PATENTS 2,702,885 2/1955 Shapiro 333/30 l l l l l I l l l l l I l l l l I l 1 as l l ,1 l l I l l l l l l l Primary Examiner-Rodney D. Bennett, Jr. Assistant ExaminerBrian C. Ribando andrney Louisgtlinger ABSTRACT: There is herein described a continuously variable electrical delay device wherein a beam of electrically charged particles impinge upon an electroacoustic delay element. By imposing a charge or electrical impulse on the surface of the delay element, an acoustic wave can be created therein. This acoustic wave and an associated electrical charge travel through the delay element to a pickoff terminal where a detectable output voltage is removed. The amount of time by which an input signal is delayed is continuously and accurately variable over a wide range of values by electronically varying the position at which the charged particle beam impinges upon the delay element with respect to the pickofi PATENTED was 1 |97| SHEET 1 BF 5 INVENTORS WILLIAM J. SOULE DAVID J. WHITNEY FIG. 2

AT T ORNE Y sum 3 OF 5 3602.767

PATENTEB was! 191:

INVENTORS WILLIAM J. SOULE DAVID J. WHlTNEY A T TORNE Y PATENTED m I97! 3.602767 SHEET '4 [IF 5 INPUT L INPUT IN VE N TORS WILLIAM J. SOULE DAVID J.WH|TNEY A T TOR/V5 Y PATENTEBAUBSIIHYI SHEET 5 [IF 5 PEG. T!

INVENTORS WILLIAM J. SOULE DAVID J. WHITNEY A T TOR/VE Y coiv'rnvuousrv VARIABLE ELEcrRoAcousTlc DELAY DEVICE BACKGROUND OF THE INVENTION delay devices.

2. Description of the Prior Art In the prior art two approaches have been taken to the problem of providing electrical. delay lines which are continuously variable. The first approach was to fabricate the delay line from two or more elements of nonpiezoelectric material. Variation in the delay time provided by such apparatus was then obtained by physically. sliding the individual delay elements relative to one another to thereby increase or decrease the path length between the input and output transducers. This approach obviously entails several drawbacks; specifically the interface between the individual-delay members may involve undesired reflections of the acoustic waves thus impairing the precision with which an input signal is delayed. Also, as when any bodies must move in contact with one another, wear occurs which again degrades the performance of the apparatus. Typically the mechanically variable delay lines of this type are of slow response and limited bandwidth. A second approach has been the electrooptical type delay line wherein variation in delay time is provided by the physical movement of an optical system with. respect to an acoustic delay line. Delay lines of this type aregenerally very expensive and retain a requirement for mechanical manipulation to vary the delay time. Further the response time of such devices in undesirably long and the range of values over which the delay time is variable is quite limited,

OBJECTS AND SUMMARY OFTHE INVENTION it is therefore a primary object of the present invention to provide a new and novel electroacoustic delay device wherein the delay time is continuously variable by electronic means.

It is another object of the present-invention to provide apparatus of the above-described character wherein the delay time is varied by deflecting a charged particle beam to impinge upon a delay element at varying distances from a pickoff means.

It is an additional object of the present invention to provide apparatus of the above-described character havinga single electroacoustic transducer as the delay element thereof.

It is a further object of the present invention to provide apparatus of the above-described-character having a very fast response time.

Itis also an object of the present invention to provide apparatus of the above-described character having an increased range of available delay time variation.

It is still another object of the present invention'to provide apparatus of the above described character for producing largev signal trains.

It is still a further object of the present invention to provide a new and novel delay line memory.

It is still an additional object of the present invention to provide. new and novel means for computer bandwidth compression.

It is yet a further object of the. present invention to provide means for producing infinite delays of input signals by recycling revolver techniques.

It is yet another object of the presentinvention to provide a continuously variable electrical delay device wherein a piezoelectric transducer includes means for producing secondary electron emission etfectsto thereby intensify the signal produced therein by impingement of electrically charged particles. I

It is also an object of the present invention to provide apparatus of the above-described character wherein a plurality of charged. particle, sources and a plurality of pickoff means are employed to simultaneously delay a plurality of input signals.

In carrying out the present invention, a continuously variable electrical delay device comprises an electroacoustic delay element having for example a piezoelectric transducer, a source of electrically charged particles such as an electron gun, means such as electrostatic deflection plates for directing charged particles and output terminals coupled to the delay element; all of which are disposed within a protective envelo e which may be either evacuated or filled with a suitable gas. The charged particle source, when activated by an input signal, produces a focused beam of charged particles which is deflected such as to impinge upon the electroacoustic delay element at a point remote from an output terminal. The incidence of the charged particles on the delay element generates an acoustic wave therein which travels at a known, fixed velocity through the delay element to a pickofi point where an electrical signal is recovered. It will be apparent that, since the velocity of sound in a given delay element material is precisely known the delay time provided by the apparatus of the present invention may easily be varied to any desired value by deflecting the charged particle beam such that it is incident on the delay element at a distance from the pickoff determined by the product of the delay time desired and the acoustic velocity. Thus the delay time is continuously and accurately variable solely by electronic means.

The foregoing as well as other objects, features and advantages of the present invention will become more apparent from the detailed discussion taken in conjunction with the accompanying drawings. The scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a continuously variable delay device constructed in accordance with the principles ofthe present invention.

FIG. 2 schematically illustrates another embodiment of the delay element of the present invention having a secondary emission enhancement means.

FIG. 3 is a schematic view of a third embodiment of the delay element of the present invention wherein a very long delay element is provided.

FIG. 4 illustrates a further embodiment of the present invention incorporating position modulation of the charged particle beam.

FIG. 5 is a schematic representation of an embodiment of the present invention having a plurality of delay elements.

FIG. 6 schematically illustrates an embodiment of the present invention wherein a plurality of input signals are simultaneously delayed.

FIG. 7 illustrates a return beam delay device constructed according to the principles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings and in particular to FIG. 1 there is shown a schematic view of a continuously variable electrical delay device fabricated according to the principles of the present invention. The device comprises a source of charged particles generally indicated at 10, a particle deflec tion system 12 and a delay element 14. The charged particle source 10 is illustrated as a conventional electron gun comprising a cathode 16, a grid 18 and an anode assembly 20. An accelerating voltage from a power supply 22 is applied across the cathode l6 and anode assembly 20. A source of input signals 24 is coupled across the cathode l6 and grid 18 to thereby intensity or amplitude modulate the beam of charged particles 26.

The deflection system 12 may conveniently be in the form of conventional longitudinal and transverse electrostatic deflection plates 28 and 30 and 32 and 34 which are coupled to longitudinal and transverse power supplies 36 and 38 respectively. Also amenable for use in the practice of the present invention are magnetic deflection yokes of the conventional type known in the art.

The delay element 14 comprises an electroacoustic transducer 15 which will be described more fully hereinafter disposed on a ground plane 40 and having pickoff terminals 42 and 44 at either or both ends thereof. Acoustic terminations 46 and 48, which may be formed of lead, tin, quartz or any other suitable material and will also be discussed more fully hereinbelow, are disposed at the ends of the transducer next to the pickoff terminals. All of the above elements are disposed within a housing 50, only a portion of which is shown, within which there is a preselected environmental condition. In the present embodiment, this environment is substantially a vacuum. The housing 50 is preferably made of glass, however, ceramic materials or metals are equally suitable The delay device thus is of the general configuration of a cathode ray tube.

In the operation of the delay device of FIG. 1 a signal to be delayed is applied from the signal source 24 across the cathode 16 and grid 18. A DC voltage from a power supply 22 coupled across the cathode 16 and anode assembly accelerates the charged particles from the cathode 16, through the anode assembly 20 whereby the charged particles are focused into a narrow beam, and toward the deflection system 12. The input signal thus intensity modulates the particle beam 26.

The deflection plates 28, 30, 32 and 34 are coupled to variable voltage sources 36 and 38. In the present embodiment the plates 32 and 34 provide transverse deflection of the particle beam 26 such that the beam will impinge upon the transducer 15. The deflection plates 28 and cause deflection of the particle beam 26 along the longitudinal axis of the transducer 15 and cause the beam to impinge upon the transducer at a predetermined distance from the terminal strips 42 and 44. The amount of delay imparted to an input signal is thus determined by the amount of longitudinal deflection of the particle beam 26 and is continuously dependent upon the voltage applied to the deflection plates 28 and 30 from the variable voltage source 36.

When the charged particles in the beam 26 impinge upon the transducer 15 an electrical charge is built up at the spot 52 and an electric field through the transducer 15 is produced. Under the influence of the electric field the transducer 15 undergoes acoustic resonance resulting in an acoustic wave traveling away from the spot 52 in both directions along the longitudinal axis of the transducer. As the acoustic wave travels through the transducer an electric charge is developed on the surface thereof and travels with the acoustic wave. When the acoustic wave reaches the terminals 42 and 44, the charge produced on the surface of the transducer due to the acoustic wave is removed via leads 54 an 56 respectively. The acoustic terminations 46 and 48 absorb the acoustic wave which passes beyond the terminal strips 42 and 44 and thus prevent reflection of the acoustic wave back through the transducer 15. This prevents the occurrence of false delayed signals which could occur if such reflections were permitted. The acoustic terminations 46 and 48 also preclude the mixing of a desired acoustic wave with reflections which would serve to distort the signal.

Since the time required for the acoustic wave to travel through the transducer medium is of a known, fixed value, and since the longitudinal deflection of the beam is continuously controllable by means of the voltage applied to the longitudinal deflection plates, there is imparted to the beam (and thus to the incoming signal) a predetermined delay which may be varied by varying the voltage applied to the longitudinal deflection plates. It will be apparent that the delayed signal can be obtained from either terminal 42 or terminal 44, or from both if more than one delayed signal is required.

The electron source cathode 16 may be made of directly or indirectly heated oxide-type materials, examples of which are barium oxide, calcium oxide, and strontium oxide. Heated thoriated tungsten cathodes may also be employed, as can any type of material which, by means of its thermionic work function and its temperature, produces efficient and useful emission of electrons. Other types of electron sources which may also be employed are those commonly referred to as cold cathodes," whose basic electronic properties, in conjunction with a suitable electrical field intensity impressed thereon, may be induced to emit electrons without necessitating heating of the source. Included within the category of cold cathodes are those materials which may also require the use of external or internal radiation, such as isotopic or ultraviolet. Materials which may also be utilized as electron sources are those of the photoelectric type, wherein electron emission is obtained not by employing heating or the use of electric fields but merely by the transfer of energy between an electromagnetic quanta and a free or bound electron within the photoelectric material itself. Also, there are some materials which produce useful electron emission due to their inherent geometrical configuration when disposed within a suitable electric or magnetic field.

The delay device may also be constructed utilizing ion sources similar to those described hereinabove with reference to the electron sources. When constructed in the above manner, he vacuum environment is replaced by a gaseous one. If the polarity of the biasing and power voltages remains the same, then negative ions will be forced to impinge upon the transducer; if the voltages are reversed, then positive ions will be forced to impinge upon the transducer. In either case, the operation and elements required therefor will be the same as previously discussed, wherein the delay device employs an electron source.

As described hereinabove, the transducer 15 is of the electroacoustic type and is generally formulated from a material which, under the influence of an electrical impulse, undergoes acoustic resonance to form an acoustic wave which travels from the impulse point to other points within the transducer. Included within the above types of materials are those which, by means of heating or magnetic effect, produce an acoustic or slow wave" effect. Generally, materials which can be utilized as acoustic transducers exhibit one or more of the following properties: i.e., they are piezoelectric, pyroelectric, thermoelastic, piezomagnetic, magnetoelastic, thermomagnetic, electrostatic or ferroelectric. Examples of materials which exhibit the piezoelectric, pyroelectric and thermoelastic properties are crystalline quartz and cadmium sulfide. Examples of materials which exhibit the ferroelectric property are lead zirconate, barium titanate and sodium potassium niobate. An examples of material which exhibits the magnetoelastic property is yttrium-iron-garnet, commonly referred to as YIG.

It will be apparent to those skilled in the art that, although the delay device has hereinbefore been described as continuously variable, it is within the scope of the invention to have the tube provide a single fixed delay by having a constant voltage applied to the deflection system or by providing the deflection system with means for supplying a fixed DC voltage thereto. It will also be apparent that the present invention is also amenable for use as a recirculating delay device. One only need feed the output signal from the output terminals 42 and 44 back to the input of the charged particle source via feedback means 43 shown in phantom to thereby recirculate the signal.

FIG. 2 illustrates an alternative embodiment of an electroa'coustic delay element 14 which may be employed in a delay device of the type described above with reference to FIG. 1. Here the electroacoustic transducer 15 is again disposed on a ground plane 40. The pickoff terminal strips 42 and 44 and the acoustic terminations 46 and 48 are the same in construction and operation as described with reference to FIG. ll. In this embodiment, a thin layer of insulating material 58 having high secondary emission characteristics is disposed on the beam-incident surface of the transducer 15. This layer may be formed of such materials as potassium chloride, barium fluoride, magnesium oxide or aluminum oxide to name a few. In this manner the amplitude of the electrical impulse caused by the impingement of the charged particles is enhanced and high-intensity signals may be provided. Any secondary electrons which are emitted by the layer 58 in a direction away from the transducer are collected by means of a secondary electron collector grid 60 coupled to a source 62 of positive voltage which may in actual practice he the same source as the accelerating voltage source 22 of FIG. 1. The collection of such secondary electrons prevents their return to the transducer 15 and the resulting creation of false acoustic waves which would operate to degrade the performance of the apparatus in the same manner as reflected acoustic waves discussed above.

Also shown in FIG. 2 is a feature of the present invention whereby a plurality of signals may be simultaneously delayed and mixed. A second source of electrical input signals 63 may be applied to one of the terminals 42 or 44 and the two signals will thus be mixed in the transducer 15 and the combined signal removed from the other of the terminals 42 or 44.

FIG. 3 is a schematic representation of another embodiment of an electroacoustic delay element useful in the practice of the present invention. In this embodiment of electroacoustic transducer 15 is laid down on the ground plane 40 in the form of a spiral. It is thus possible to provide a very long physical delay element in a compact volume.

Another embodiment of the present invention s illustrated in FIG. 4 wherein similar parts are denoted by similar reference numerals. in this embodiment a DC voltage source 22 is coupled between the cathode l6 and anode l8 and a DC voltage from source 64 is coupled between the cathode l6 and grid 18. In this manner the delay device is biased such that it always remains in a conducting state. Although the voltage sources 22 and 64 have been shown separately, it is to be understood that they may in practice be a single source. A variable voltage source 36 is coupled to the transverse deflection plates 32 and 34 such that in the absence of an input signal the particle beam 26 is directed to a spot such as 52a located to one side of the transducer 15. A voltage source 38 also applies to a voltage to the longitudinal deflection plates 28 and 30 which deflects the particle beam 26 to a predetermined longitudinal distance from the output terminals 42 and 44 which is directly proportional to the delay to be imparted to an input signal.

In the operation of the apparatus of FIG. 4 the source 24.0f input signals is coupled to the transverse deflection plates 32 and 34. In the absence of an input signal the particle beam spot 52a is disposed to one side of the transducer 15 and no signal is present at the output terminals 42 and 44. The variable voltage source 38 is adjusted to provide longitudinal deflection of the particle beam to a position 52b which is the desired longitudinal distance from the output terminals 42 and 44. On the application of an input signal from the source 24 the voltage on the transverse deflection plates 32 and 34 is changed and the particle beams 26 is deflected transversely such as to impinge upon the transducer 15, for example at spot, 52. An acoustic wave is thus created in the transducer 15 in the above-described manner and the delayed signal is removed via the output terminals 42 and 44. On removal of the input signal from the transverse deflection plates 32 and 34 the particle beam spot 52 is returned to a position such as 52a transversely away from the transducer 15.

This embodiment of the present invention may also be adapted for use as a recirculating delay device by adding the feedback means 43 whereby the delayed signal is fed back to the delay device input.

FIG. 5 is a schematic illustration of another embodiment of the present invention whereby an input signal may be subjected to a plurality of delays. In this embodiment the delay.

element 14 comprises a plurality of transducers 70, 72 and 74, each of a different electroacoustic material, disposed on a ground plane 40. The acoustic waves created in these transducers will move longitudinally from the .spot of particle impingement at a velocity which is characteristic of the materials of which transducers 70, 72 and 74 are formed. Thus in the three transducer embodiment illustrated in FIG. 5 an input signal from source 24 may be subjected to as many as six individually unique delay times. The delayed signals may be removed from any or all of the output terminals 76 through 86. Acoustic terminations 88 and 90 are also provided to prevent undesired acoustic reflections.

FIG. 6 illustrates another embodiment of the present invention whereby a plurality of input signals may be simultaneously delayed and mixed; similar parts being identified by similar reference numerals. In this embodiment a plurality of particle sources 10 and 10' each having an associated deflection system 12 and 12' respectively are used in conjunction with a delay element 14. In many applications it is desirable to mix a plurality of signals. To provide this capability a first signal is applied from a first source 24 across the cathode l6 and grid 18 of the first charged particle source 10. The intensity modulated first particle beam 26 is then deflected by the first deflection system 12 to a preselected spot 52 on the transducer 15. Thus a first acoustic wave is created in the transducer and moves longitudinally therein in the above-described manner toward output terminals 42 and 44. The second particle source 10' and the associated deflection system 12' operate in a similar manner to produce and deflect a second particle beam 26 which is also intensity modulated by a second signal from source 24'. The second particle beam 26' is illustrated as being incident upon the transducer 15 at a spot 52' which is remote from the spot 52 on which the first particle beam 26 is incident. It will be apparent that the spots 52 and 52 may in actual practice be coincident if both input signals are to be delayed by the same amount of time. The acoustic waves created by the impingement of the first and second particle beams 26 and 26' thus combine in the transducer 15 and a suitably delayed and mixed electrical signal is removed from the output terminals 42 and 44. The acoustic terminations 46 and 48 are the same in construction and operation as discussed hereinabove with reference to FIG. 1. Although two particle sources 10 and 10' and two deflection systems 12 and 12 are shown with a single delay element 14 in FIG. 6 it will be apparent that the present invention provides considerable flexibility in also contemplating a plurality of sources as in FIG. 6 in combination with a plurality of delay elements as in FIG. 5.

FIG. 7 schematically illustrates what is herein termed a return beam delay device fabricated according to the principles of the present invention. Again, similar parts are identified by similar reference numerals. In this embodiment a charged particle writing beam 26 is generated by a charged particle source 10, modulated by a source of input signals 24 and deflected by the deflection system 108 such that it is incident upon the electroacoustic transducer 15. The transducer 15 is disposed on a ground plane 40, has acoustic termination 46 and 48 disposed on either end thereof and a layer 58 of secondary emission enhancement material. As discussed hereinabove the impingement of the charged particles on the transducer 15 results in an acoustic wave moving longitudinally in the transducer away from the point at which the particle beam 26 is incident. Associated with this acoustic wave is an electric charge which also travels along the surface of the transducer 15. This charge is of the same polarity as the charged particles in the beam 26. Once the acoustic wave is generated in the transducer 15 the charged particle beam may be deflected to an angular position such as 26a which corresponds to some preselected longitudinal distance, X, from the point of incidence of the writing beam 26. The acoustic wave within the transducer and the associated electric charge will travel the distance, X, from the point of writing beam impingement in a precisely known time. Thus when the charged particle reading beam 26a is deflected as shown at the time the acoustic wave passes the electric charge associated with the acoustic wave will exert a coulombic repulsive force on the particles in the beam and reflect the beam 26a back in the general direction of the particle source 10. The beam 26b returned in this manner has impressed thereon any modulation of the acoustic wave which was originally present in the input signal. A limiting aperture 100 is disposed about the charged particle source to substantially eliminate the return of charged particles in the beam 26b directly into a source 10. The return beam 26b is thus incident upon a series of particle multiplying dynodes 102a through e and then on a particle detector anode 104 where the suitably delayed signal is removed via output leads 106. Although a single charged particle source is illustrated in FIG. 7 a plurality of sources may be used as shown in FIG. 6 to thereby provide a capability for simultaneously inserting and extracting signals from the transducer.

In the return beam embodiment of the present invention a magnetic deflection system 108 is shown and is preferred. This arrangement substantially precludes interference with the beam 26:: by the return beam 26b.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described what is new and novel and desired to secure by Letters Patent, what is claimed is:

1. Apparatus for imparting a delay to an electrical input signal comprising means for producing a beam of electrically charged particles in response to said input signal,

an electroacoustic transducer having at least one output terminal connected therewith and wherein there is produced a signal in response to the impingement directly thereon of electrically charged particles which signal travels from the point of impingement to said output terminal with a predetermined velocity, and

continuously variable means for directing said beam of electrically charged particles such that it impinges upon said transducer at any preselected point thereon remote from said output terminal whereby said input signal is delayed by an amount of time proportional to the distance between said point of direct impingement and said output terminal.

2. Apparatus as recited in claim 1 wherein said apparatus is disposed within a housing having a preselected environment.

3. Apparatus as recited in claim 2 wherein said electrically charged particles are electrons, and

said environment is substantially a vacuum.

4. Apparatus as recited in claim 2 wherein said electrically charged particles are ions, and

said environment is a gas.

5. Apparatus as recited in claim 3 wherein said means for producing said electron beam comprises an electron source,

means for accelerating said electrons, and

means for focusing said electrons.

6. Apparatus as recited in claim 1 wherein said variable beam directing means comprises electrostatic deflection plates coupled to a variable source of voltage.

7. Apparatus as recited in claim 1 wherein said variable beam directing means comprises an electromagnetic deflection yoke.

8. Apparatus as recited in claim 1 wherein said transducer has a plurality of output terminals connected therewith.

9. Apparatus as recited in claim 1 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said acoustic wave is substantially precluded.

10. Apparatus as recited in claims 1 further including feedback means coupling said output terminal to said beam producing means whereby said signal is recirculated through said apparatus.

11. Apparatus as recited in claim 1 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer. 12. Apparatus as recited in claim 1 1 further including secondary charged particle collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer. 13. Apparatus as recited in claim 1 wherein said transducer is disposed in a plane spiral configuration whereby an extended length transducer is provided in a minimum volume. 14. Apparatus as recited in claim 1 wherein a plurality of parallel transducers are provided whereby said input signal may be subjected to a plurality of delays. 15. Apparatus as recited in claim 14 wherein each of said transducers are formed of a different electroacoustic material having a unique acoustic velocity. 16. Apparatus as recited in claim 1 further including an additional signal input means connected with said transducer and having additional input signal coupled thereto, whereby said electrical input signal and said additional input signal are combined in said transducer and said combined signal is presented at said output terminal. 17. Apparatus as recited in claim 1 wherein a plurality of beam producing means are provided, each of said means producing a beam of electrically charged particles in response to one of a plurality of electrical input signals, and means for directing each of said beams such that each beam impinges upon said transducer at a preselected point thereon remote from said output terminal whereby a plurality of input signals are delayed and combined within said transducer. 18. Apparatus for imparting a delay to an electrical input signal comprising means for producing a substantially continuous beam of electrically charged particles, an electroacoustic transducer having at least one output terminal connected therewith, and wherein there is produced a signal in response to the impingement directly thereon of electrically charged particles which signal travels from the point of impingement to said output terminal with a predetermined velocity, and continuously variable means for directing said beam of electrically charged particles having said input signal coupled thereto, and operative to direct said particles transversely of said transducer in the absence of an input signal and to direct said particles in response to said input signal such that they impinge upon said transducer at any preselected point thereon remote from said output terminal whereby said input signal is delayed by an amount of time proportional to the distance between said point of direct impingement and said output terminal. 19. Apparatus recited in claim 18 wherein said apparatus is disposed within a housing having a preselected environment.

20. Apparatus as recited in claim 19 wherein said electrically charged particles are electrons, and said environment is substantially a vacuum. 21. Apparatus as recited in claim 19 wherein said electrically charged particles are ions, and said environment is a gas. 22. Apparatus as recited in claim 20 wherein said means for producing said electron beam comprises an electron source means for accelerating said electrons, and means for focusing said electrons. 23. Apparatus as recited in claim 18 wherein said variable beam directing means comprises transverse and longitudinal electrostatic deflection plates, said transverse deflection plates having said input signal coupled thereto, and

said longitudinal deflection plates being coupled to a variable source of voltage. 1

24. Apparatus as recited in claim 18 wherein said variable beam directing means comprises an electromagnetic deflection yoke.

25. Apparatus as recited in claim 18 wherein said transducer has a plurality of output terminals connected therewith.

26. Apparatus as recited in claim 18 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said acoustic wave is substantially precluded. 1

27. Apparatus as recited in claim 18 further including feedback means coupling said output terminal to said beam producing means whereby said signal is recirculated through said apparatus.

28. Apparatus as recited in claim 18 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer.

29. Apparatus as recited in claim 28 further including a secondary emission collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer.

30. Apparatus as recited in claim 18 wherein said transducer is disposed in a plane spiral configuration whereby an extended length transducer is provided in a minimum volume.

.31. Apparatus as recited in claim 18 wherein a plurality of parallel transducers are provided whereby said input signal may be subjected to a plurality of delays.

32. Apparatus as recited in claim 31 wherein each of said transducers are formed of a different'electroacoustic material having a unique acoustic velocity.

33. Apparatus as recited in claim 18 further including an additional signal input means connected with said transducer and having an additional input signal coupled thereto whereby said electrical input signal and said additional input signal are combined in said transducer and said combined signal is presented at said output terminal.

34. Apparatus as recited in claim 18 wherein a plurality of beam producing means are provided,

each of said means producing a beam of electrically charged particles in response to one of a plurality of electrical input signals, and

means for directing each of said beams such that each beam impinges upon said transducer at a preselected point thereon remote from said output terminal,

whereby a plurality of input signals are delayed and combined within said transducer. 35. Apparatus for imparting a delay to an electrical input signal comprising means for producing a beam of electrically charged particles in response to said input signal,

. an electroacoustic transducer wherein there is produced a signal in response to the impingement thereon of electrically charged particles which signal travels therein from the point of said impingement to said output terminal with a predetermined velocity,

continuously variable means for selectively directing said beam of electrically charged particles toward said transducer at either of preselected first and second points thereon remote from said output terminal and from each other whereby the sequential direction of said beam to said first and second points causes said electrically charged particles to be reflected from said second point by said signal travelling in said transducer from said first point through said second point, and

means for detecting said reflected charged particles and producing an out ut signal in response thereto which output signal correspon s to said input signal delayed by an amount of time proportional to the distance between said first and second point. 1

36. Apparatus as recited in claim 35 wherein said apparatus is disposed within a housing having a preselected environment.

37. Apparatus as recited in claim 36 wherein said electrically particles are electrons, and

said environment is substantially a vacuum.

38. Apparatus as recited in claim 36 wherein said electrically charged particles are ions, and

said environment is a gas.

39. Apparatus as recited in claim 37 wherein said means for producing said electron beam comprises an electron source,

means for accelerating said electrons, and

means for focusing said electrons.

40. Apparatus as recited in claim 35 wherein said variable beam directing means comprises electrostatic deflection plates coupled to a variable source of voltage.

41. Apparatus as recited in claim 35 wherein said variable beam directing means comprises an electromagnetic deflection yoke.

42. Apparatus as recited in claim 37 wherein detecting means comprises a plurality of electron multiplying dynodes disposed adjacent said beam producing means, and

an electron sensitive anode producing an output signal in response to said reflected electrically charged particles.

43. Apparatus as recited in claim 35 wherein said acoustic wave has associated therewith an electrical charge of the same polarity as said electrically charged particles whereby reflection of said electrically charged particles from said point is provided by coulombic forces 44. Apparatus as recited in claim 43 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said wave is substantially precluded.

45. Apparatus as recited in claim 35 further including feedback means coupling said detecting means to said beam producing means,

whereby said signal is recirculated through said apparatus.

46. Apparatus as recited in claim 35 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer.

47. Apparatus as recited in claim 46 further including secondary charged particle collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer. 

1. Apparatus for imparting a delay to an electrical input signal comprising means for producing a beam of electrically charged particles in response to said input signal, an electroacoustic transducer having at least one output terminal connected therewith and wherein there is produced a signal in response to the impingement directly thereon of electrically charged particles which signal travels from the point of impingement to said output terminal with a predetermined velocity, and continuously variable means for directing said beam of electrically charged particles such that it impinges upon said transducer at any preselected point thereon remote from said output terminal whereby said input signal is delayed by an amount of time proportional to the distance between said point of direct impingement and said output terminal.
 2. Apparatus as recited in claim 1 wherein said apparatus is disposed within a housing having a preselected environment.
 3. Apparatus as recited in claim 2 wherein said electrically charged particles are electrons, and said environment is substantially a vacuum.
 4. Apparatus as recited in claim 2 wherein said electrically charged particles are ions, and said environment is a gas.
 5. Apparatus as recited in claim 3 wherein said means for producing said electron beam comprises an electron source, means for accelerating said electrons, and means for focusing said electrons.
 6. Apparatus as recited in claim 1 wherein said variable beam directing means comprises electrostatic deflection plates coupled to a variable source of voltage.
 7. Apparatus as recited in claim 1 wherein said variable beam directing means comprises an electromagnetic deflection yoke.
 8. Apparatus as recited in claim 1 wherein said transducer has a plurality of output terminals connected therewith.
 9. Apparatus as recited in claim 1 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said acoustic wave is substantially precluded.
 10. Apparatus as recited in claims 1 further including feedback means coupling said output terminal to said beam producing means whereby said signal is recirculated through said apparatus.
 11. Apparatus as recited in claim 1 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer.
 12. Apparatus as recited in claim 11 further including secondary charged particle collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer.
 13. Apparatus as recited in claim 1 wherein said transducer is disposed in a plane spiral configuration whereby an extended length transducer is provided in a minimum volume.
 14. Apparatus as recited in claim 1 wherein a plurality of parallel transducers are provided whereby said input signal may be subjected to a plurality of delays.
 15. Apparatus as recited in claim 14 wherein each of said transducers are formed of a different electroacoustic material having a unique acoustic velocity.
 16. Apparatus as recited in claim 1 further including an additional signal input means connected with said transducer and having additional input signal coupled thereto, whereby said electrical input signal and said additional input signal are combined in said transducer and said combined signal is presented at said output terminal.
 17. Apparatus as recited in claim 1 wherein a plurality of beam producing means are provided, each of said means producing a beam of electrically charged particles in response to one of a plurality of electrical input signals, and means for directing each of said beams such that each beam impinges upon said transducer at a preselected point thereon remote from said output terminal whereby a plurality of input signals are delayed and combined within said transducer.
 18. Apparatus for imparting a delay to an electrical input signal comprising means for producing a substantially continuous beam of electrically charged particles, an electroacoustic transducer having at least one output terminal connected therewith, and wherein there is producEd a signal in response to the impingement directly thereon of electrically charged particles which signal travels from the point of impingement to said output terminal with a predetermined velocity, and continuously variable means for directing said beam of electrically charged particles having said input signal coupled thereto, and operative to direct said particles transversely of said transducer in the absence of an input signal and to direct said particles in response to said input signal such that they impinge upon said transducer at any preselected point thereon remote from said output terminal whereby said input signal is delayed by an amount of time proportional to the distance between said point of direct impingement and said output terminal.
 19. Apparatus recited in claim 18 wherein said apparatus is disposed within a housing having a preselected environment.
 20. Apparatus as recited in claim 19 wherein said electrically charged particles are electrons, and said environment is substantially a vacuum.
 21. Apparatus as recited in claim 19 wherein said electrically charged particles are ions, and said environment is a gas.
 22. Apparatus as recited in claim 20 wherein said means for producing said electron beam comprises an electron source means for accelerating said electrons, and means for focusing said electrons.
 23. Apparatus as recited in claim 18 wherein said variable beam directing means comprises transverse and longitudinal electrostatic deflection plates, said transverse deflection plates having said input signal coupled thereto, and said longitudinal deflection plates being coupled to a variable source of voltage.
 24. Apparatus as recited in claim 18 wherein said variable beam directing means comprises an electromagnetic deflection yoke.
 25. Apparatus as recited in claim 18 wherein said transducer has a plurality of output terminals connected therewith.
 26. Apparatus as recited in claim 18 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said acoustic wave is substantially precluded.
 27. Apparatus as recited in claim 18 further including feedback means coupling said output terminal to said beam producing means whereby said signal is recirculated through said apparatus.
 28. Apparatus as recited in claim 18 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer.
 29. Apparatus as recited in claim 28 further including a secondary emission collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer.
 30. Apparatus as recited in claim 18 wherein said transducer is disposed in a plane spiral configuration whereby an extended length transducer is provided in a minimum volume.
 31. Apparatus as recited in claim 18 wherein a plurality of parallel transducers are provided whereby said input signal may be subjected to a plurality of delays.
 32. Apparatus as recited in claim 31 wherein each of said transducers are formed of a different electroacoustic material having a unique acoustic velocity.
 33. Apparatus as recited in claim 18 further including an additional signal input means connected with said transducer and having an additional input signal coupled thereto whereby said electrical input signal and said additional input signal are combined in said transducer and said combined signal is presented at said output terminal.
 34. Apparatus as recited in claim 18 wherein a plurality of beam producing means are provided, each of said means producing a beam of electrically charged particles in response to one of a plurality of electrical input signals, and means for directing each of said beams such that each beam impinges upon said transducer at a preselected point thereon remote from said output terminal, whereby a plurality of input signals are delayed and combined within said transducer.
 35. Apparatus for imparting a delay to an electrical input signal comprising means for producing a beam of electrically charged particles in response to said input signal, an electroacoustic transducer wherein there is produced a signal in response to the impingement thereon of electrically charged particles which signal travels therein from the point of said impingement to said output terminal with a predetermined velocity, continuously variable means for selectively directing said beam of electrically charged particles toward said transducer at either of preselected first and second points thereon remote from said output terminal and from each other whereby the sequential direction of said beam to said first and second points causes said electrically charged particles to be reflected from said second point by said signal travelling in said transducer from said first point through said second point, and means for detecting said reflected charged particles and producing an output signal in response thereto which output signal corresponds to said input signal delayed by an amount of time proportional to the distance between said first and second point.
 36. Apparatus as recited in claim 35 wherein said apparatus is disposed within a housing having a preselected environment.
 37. Apparatus as recited in claim 36 wherein said electrically particles are electrons, and said environment is substantially a vacuum.
 38. Apparatus as recited in claim 36 wherein said electrically charged particles are ions, and said environment is a gas.
 39. Apparatus as recited in claim 37 wherein said means for producing said electron beam comprises an electron source, means for accelerating said electrons, and means for focusing said electrons.
 40. Apparatus as recited in claim 35 wherein said variable beam directing means comprises electrostatic deflection plates coupled to a variable source of voltage.
 41. Apparatus as recited in claim 35 wherein said variable beam directing means comprises an electromagnetic deflection yoke.
 42. Apparatus as recited in claim 37 wherein detecting means comprises a plurality of electron multiplying dynodes disposed adjacent said beam producing means, and an electron sensitive anode producing an output signal in response to said reflected electrically charged particles.
 43. Apparatus as recited in claim 35 wherein said acoustic wave has associated therewith an electrical charge of the same polarity as said electrically charged particles whereby reflection of said electrically charged particles from said point is provided by coulombic forces
 44. Apparatus as recited in claim 43 further including acoustic terminations disposed at the ends of said transducer whereby said acoustic wave is absorbed after having travelled to the end of said transducer and reflection of said wave is substantially precluded.
 45. Apparatus as recited in claim 35 further including feedback means coupling said detecting means to said beam producing means, whereby said signal is recirculated through said apparatus.
 46. Apparatus as recited in claim 35 further including a layer of secondary emission enhancement material disposed on the beam incident surface of said transducer.
 47. Apparatus as recited in claim 46 further including secondary charged particle collection means whereby charged particles emitted by said layer in a direction away from said transducer are substantially prevented from returning to said transducer. 